Let me preface this by saying this didn’t / doesn’t affect me at all and is incredibly low stakes, but I’m a nosy bugger and want to know what was going on!
I was in a large shopping centre today waiting to speak to customer services. In front of me was a woman who wanted to buy vouchers (you can purchase generic vouchers for the shopping centre which can be used in any shop). She bought £1000 of vouchers using cash from an envelope which honestly must have had thousands of pounds in cash inside. It took absolutely ages because they had to get a manager to check the notes.
My friend thought she was laundering drugs money, but I think it was undeclared income and she was buying vouchers so that she could get Christmas presents without having to have the money to pay for them in her account. A few shops in that centre are cashless now, or I suppose she could just have paid cash.
Am I unduly suspicious? Maybe there’s a totally legitimate reason why you would do this, but I couldn’t think of one!